The present invention relates to a device for the formation of skeined sections on thin metallic wires particularly suited for the production of end sections of electrical coil windings.
In some industrial applications there is a need for production of very thin metallic wire sections wound in stranded skeins. One of these applications is the production of electrical coils made with very thin wire (thickness less than 0.2 mm) whose winding should display thicker end parts achieved by skeining the winding wire.
Production of these coils requires the solution of various technical problems intended mainly to achieve:
accurately gauged tensioning of the wire during its winding on the coil and during formation of the skeined ends to prevent irregularity in the winding and in the ends and possible abrasion of the thin insulating film covering the wire,
skeined sections bearing slots with very small dimensions at their ends,
fast, gauged recovery of any oversupplying of the wire (xe2x80x98excessesxe2x80x99) towards the coil winder which might occur during winding because of momentary slowing, stopping or reversal of winder, and
correct positioning of the skeined ends on the finished coil.
Known devices for the formation of skeins on thin metallic wires for electrical coil windings are rather slow and complicated and with systems for wire tensioning, recovery of any excesses and positioning of the skeins on the finished coils, which entail drawbacks as specified below.
The purpose of the present invention is realization of a very simple, fast and reliable device for the formation of thin metallic wire skeins free of the above mentioned shortcomings of the prior art.
In accordance with a preferred embodiment the skein formation device also allows recovery of any wire excesses which might occur during coil winding.
The device for the formation of skeined sections on thin metallic wires according to the present invention is of the type in which the wire to be skeined extends from an inlet point (9) to an anchor point (15) and is placed under traction by a wire-tightening device (2), said device being characterized in that a branch of said wire emerging from said anchor point is sent to a wire-tightening device (8) controlled by a electronic control system which controls the skeining operation, in said wire-tightener being present the following parts:
a first pulley (28) on which winds said emerging wire and which is mounted on a second shaft connected to an electromagnetic brake (29) with electromagnetic hysteresis rotated in a direction contrary to the motion given the pulley by the wire,
a second pulley (27) located above the first pulley (28) and mounted in an idling manner on a pin in turn mounted on a cell (30) sensitive to the load bearing on the pin and sending a signal signifying the load to the control system which regulates the braking action of the brake with hysteresis in such a manner as to maintain the load at a predetermined value,
the path of the wire coming from the above mentioned snub pulley being characterized in that it descends on a first side of the above mentioned second pulley (27) and then winds on the first pulley (28) and returns to the second side of the second pulley (27) on which it winds for 180xc2x0 and then again descends on the first side towards a wire winding machine (5) located downstream.